Since HiRISE first started finding avalanches on Mars, we have continued searching for them in the most likely places: steep cliffs at the edges of the layered deposits at the North Pole.

These layers are exposed in the scarp face that cuts through them diagonally across this subimage. The bright smoother material at the lower left is at the top of the cliff, and here we have caught another avalanche as it falls down the steep slope towards the upper right of the image.

A large (approximately 200 meters or 600 feet across) cloud of reddish dust has been kicked up at the base of the scarp. Fine tendrils of bright wisps are visible farther up the cliff face—these may be individual falls of material, before spreading out as the avalanche plummets downward.

This might allow scientists to figure out the exact location of the start of the avalanche; for example, which layer it originally came from and how far it fell. This information will help narrow down what triggers these falls: is it seasonal temperature changes in the ice layers, gusts of wind passing over loosened rocks in steep slopes, or something else entirely?

In the upcoming season of spring in the Northern hemisphere, HiRISE will be searching for even more of these events in order to better understand when and where they happen, and why.

Written by: Ingrid Daubar (26 October 2011)

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Postscript
For information about NASA and agency programs on the Web, visit: http://www.nasa.gov.
NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance
Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and
built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.
The image data were processed using the U.S. Geological Survey’s ISIS3 software.